package cn.itcast.n8;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

import static cn.itcast.n2.util.Sleeper.sleep;

/**
 * className: TestAqs
 * description:
 * date: 2023/3/6 0006-14:00
 * <p>
 * project: concurrent
 * package: cn.itcast.n8
 * email: 1085844536@qq.com
 * version:
 *
 * @author WangGuojian
 */
@Slf4j(topic = "c.TestAqs")
public class TestAqs {

    public static void main(String[] args) {
        MyLock lock = new MyLock();
        new Thread(() -> {
            lock.lock();
            log.debug("locking...");
            lock.lock();
            log.debug("locking...");
            try {
                log.debug("locking...");
                sleep(1);
            } finally {
                log.debug("unlocking...");
                lock.unlock();
            }
        }, "t1").start();

        // new Thread(() -> {
        //     lock.lock();
        //     try {
        //         log.debug("locking...");
        //     } finally {
        //         log.debug("unlocking...");
        //         lock.unlock();
        //     }
        // }, "t2").start();
    }
}

/**
 * 自定义锁(不可重入锁)
 */
class MyLock implements Lock {

    /**
     * 独占锁 同步器类
     */
    static class MySync extends AbstractQueuedSynchronizer {

        @Override
        protected boolean tryAcquire(int arg) {
            if (compareAndSetState(0, 1)) {
                // 加上了锁，并设置 owner 为当前线程
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }

        @Override
        protected boolean tryRelease(int arg) {
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }

        /**
         * 是否持有独占锁
         *
         * @return {@link Boolean}
         */
        @Override
        protected boolean isHeldExclusively() {
            return getState() == 1;
        }

        public Condition newCondition() {
            return new ConditionObject();
        }
    }

    private final MySync sync = new MySync();

    /**
     * 加锁
     */
    @Override
    public void lock() {
        sync.acquire(1);
    }

    /**
     * 加锁 可打断
     *
     * @throws InterruptedException e
     */
    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);
    }

    /**
     * 尝试加锁(一次)
     *
     * @return {@link Boolean}
     */
    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }


    /**
     * 尝试加锁 带超时
     *
     * @param time {@link Long} the maximum time to wait for the lock
     * @param unit {@link TimeUnit} the time unit of the {@code time} argument
     * @return {@link Boolean}
     * @throws InterruptedException e
     */
    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1, unit.toNanos(time));
    }

    /**
     * 解锁
     */
    @Override
    public void unlock() {
        sync.release(1);
    }

    /**
     * 创建条件变量
     *
     * @return {@link Condition}
     */
    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }
}
